Embodiments of the inventive concept described herein relate to a structure of a photonic phased array antenna, and more particularly, relate to an apparatus for forming a light beam in a narrow region due to light wave interference by controlling the phases of light waves supplied to each nanophotonic radiator disposed in an array to radiate light waves into free space.
A photonic phased array antenna is used as a light source for scanning a light beam to scan an image for an autonomous car or a robot. For such an application, preferable performances, such as a small size, high light beam radiation efficiency, a fine beam formation, a large beam scanning range, and a rapid beam scanning speed, are required to the photonic phased array antenna. Thus, to first achieve miniaturization, there is a need to propose a nanophotonics-based photonic phased array antenna using a semiconductor material. When a nanophotonics-based photonic phased array antenna using a semiconductor material is to be implemented, since a size of the device is small, there may be complex limitations to secure various performances.
There has been proposed a nanophotonics-based photonic phased array antenna disclosed in US Patent Application No. 2014/0192394 A1, where phase control photonic devices are integrated in matrix. The photonic passed array antenna according to the related art controls the phase of a light wave by using a principle of varying a refractive index based on a thermos-optic effect. According to the invention disclosed in US Patent Application No. 2014/0192394 A1, an optical delay line is installed at a front end of an antenna, and current is supplied to the optical line to heat the optical delay line. When the temperature of the optical delay line is increased as the optical delay line is heated, the refractive index of the optical delay line is increased according to the thermos-optic effect, so that the phase of the light wave passing through the optical delay line is varied. However, since the invention utilizes the thermos-optic effect, the power consumed to heat a semiconductor element is great, and the control speed is slow.
The disposal of a light wave supply line is an important design parameter of the phased array antenna. The invention employs a direct distribution scheme of supplying a light wave to unit antenna devices arrayed in a matrix. In other words, according to the direct distribution scheme, a light wave is injected to a linear optical waveguide, several optical couplers are installed on side surface of the liner optical waveguide, and optical power is sequentially extracted from each optical coupler such that the optical power is supplied to a unit antenna device. However, since the direct distribution scheme extracts a part of the optical power which is left over after the power is distributed to a preceding unit device in order to supply the extracted power to a next unit device, it is difficult to supply unit optical power to each unit device.